Seismology for the fine structure in the sun's oscillations varying with its activity cycle

Abstract

We inverted the symmetric part of the fine structure in the 1986 and 1988 solar oscillation data of Libbrecht and Woodard to find statistically significant evidence for a steady megagauss toroidal field at the bottom of the convective envelope. We confirm the sizable amplitude of a cycle-dependent near-surface perturbation which we argue has its origin in the fibril field.